Alternators for use in the electrical art are most often of the radial-gap type wherein a rotor mounted on a rotatable shaft is positioned within a generally cylindrical housing containing a winding or windings. The rotor carries permanent magnets and, when the rotor is caused to rotate on the axis of the machine, a voltage is generated in the surrounding winding unit. In another version of the radial-gap alternator, the rotor carries the windings and the magnets are positioned within the surrounding stator. In this construction, slip rings are required to take the induced voltage from the rotor.
The above-described radial-gap alternators can be rather large when it is desired to produce relatively high voltages/currents. Accordingly, they are expensive to construct and they must be driven by rather sizeable motors. Often the particular application dictates small size; therefore, these radial-gap alternators are not suitable.
Another type of alternator that has been shown to have advantages, particularly for producing a relatively high horsepower in small sizes, is that referred to as axial-gap alternators. In these devices, a disk-type rotor is positioned proximate a fixed disk-type stator (or a pair of stators, one on each side of the rotor). Permanent magnets are imbedded in the rotor such that as it is rotated by a motor, for example, voltages are generated within the stator. This type of device eliminates the need for slip-rings, and can be operated at substantially higher rotational speeds. Since the horsepower output is related to speed of rotation, this higher rotational speed generates a higher horsepower for a given size machine. Typically the rotational speed is several thousand RPM (e.g., 15,000)
Several axial-gap permanent magnet machines have been disclosed in the prior art. One such machine is described and claimed in U.S. Pat. No. 4,358,693 issued to D. L. Palmer, et al, on Nov. 9, 1982. This device is a magnetic motor having a plurality of stators with a plurality of rotors (preferably one more rotor than stator). The rotors contain a plurality of permanent magnets with their poles alternating in polarity. The windings on each stator are arranged in two sets, and a distributor cycles current to the sets so that each set reverses polarity each successive time it is charged. The construction permits the use of both poles of the magnets to provide driving forces.
Another of the prior art axial-gap devices is described and claimed in U.S. Pat. No. 4,371,801 issued to E. Richter on Feb. 1, 1983. In this device rotor disks support permanent magnets oriented to direct flux axially through the machine, and multiple stator disks are provided having distributed multi-phase windings. Means are provided to rotate one of the stator disks (relative to the other stator disks) to cause misalignment of windings on adjacent disks having the same phase. By controlling the degree of phase misalignment, the output voltage of a generator (or power factor of a motor) may be controlled.
Although the '801 device has a plurality of stators, there is no discussion of using the different stators to drive individual loads. However, even if one should attempt to accomplish the supply to different loads, magnetic fluctuations coupled from one load upon the generator would affect the voltage being supplied to the other load(s). For example, if one load is cycled off and on regularly (or irregularly), the voltage/current impulses produced by the same would be sensed in all of the stators of the machine. Such impulses, due to changes in the magnetic loading of the common magnetic material, often would be detrimental to loads being energized from those other stators. This effect would be observed using other known multiple stator machines.
Other typical references that are deemed to be related to this art are U.S. Pat. Nos. 3,428,840 issued to W. Kober on Feb. 18, 1969; 4,394,594 issued to F. Schmider on July 19, 1983; and 4,605,874 issued to E. Whitely on Aug. 12, 1986. None of these references teach the idea of connecting the different stators to separate loads and/or the isolating of different loads if so connected.
Accordingly, it is an object of the present invention to provide an axial gap generator having a plurality of magnetically-isolated stators wherein each of said stators can be used to power different loads without the conditions of one load affecting performance of other loads.
It is another object of the present invention to provide a high speed axial gap generator having at least one rotor interposed between two stators, the rotor having spaced-apart permanent magnets on each surface of the rotor to thereby face the stators whereby each of the stators can provide power to independent loads, with a magnetic barrier between the layers of magnets of the rotor so as to magnetically isolate each stator and thus electrically isolate each load.
A further object of the present invention is to provide a high speed axial gap generator having a plurality (N in number) of spaced-apart disk-type rotors mounted on a rotatable shaft, with these rotors interposed between a plurality of disk-type stators (at least N+1 in number), with each of the rotors having spaced-apart permanent magnets on each surface facing the stators, with a magnetic barrier between the layers of magnets of each rotor so as to magnetically isolate the stators and thus electrically isolate any loads supplied by those stators.
These and other objects of the present invention will become apparent upon a consideration of the drawings identified hereinafter, and their complete description.